Describe the structure of the lungs as body organs of gas exchange

When we breathe in, air moves down the trachea (wind pipe). This then branches off into the right and left bronchus which branch into further narrower tubes called the bronchioles. The windpipe and bronchus are supported and held open by rings of cartilage. At the end of the bronchioles are the the alveoli (air sacs) and this is where gases are exchanged with the blood